Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
Greg Mirsky <gregimirsky@gmail.com> Thu, 22 August 2019 23:41 UTC
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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Thu, 22 Aug 2019 16:41:10 -0700
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To: Tom Herbert <tom@quantonium.net>
Cc: "OU, Heidi" <heidi.ou@alibaba-inc.com>, "draft-ietf-ippm-ioam-data@ietf.org" <draft-ietf-ippm-ioam-data@ietf.org>, IETF IPPM WG <ippm@ietf.org>, Hugh Holbrook <holbrook@arista.com>, Anoop Ghanwani <Anoop.Ghanwani@dell.com>, Surendra Anubolu <surendra.anubolu@broadcom.com>
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Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06
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Hi Tom, I think that the right solution to the problem of collecting telemetry information as experienced by a data packet is to disconnect origination of such information and transporting it. An iOAM packet may be used as a trigger to collect the required data on a node. But the same packet doesn't have to transport that information. That could be done either using Postcard-based Telemetry <https://datatracker.ietf.org/doc/draft-song-ippm-postcard-based-telemetry/> or Hybrid Two-Step <https://datatracker.ietf.org/doc/draft-mirsky-ippm-hybrid-two-step/>methods. In that case, IP options provide sufficient space to encode the profile of telemetry data to collect on a node. Regards, Greg On Thu, Aug 22, 2019 at 12:34 PM Tom Herbert <tom@quantonium.net> wrote: > On Thu, Aug 22, 2019 at 12:21 PM OU, Heidi <heidi.ou@alibaba-inc.com> > wrote: > > > > Hi Frank, > > > > > > > > I also have a question on the encapsulation: If you can get a new > ethertype for IOAM, why not insert IOAM data directly after layer2 MAC? > instead of adding a GRE header for IOAM. > > > Because, we need a packet format that is compatible with existing > network devices. In light of that, GRE is more preferable than using > the new Ethertype directly in an Ethernet frame. There will also be > similar arguments made for using GRE/IP, and UDP encapsulation over > IP, and there was even a proposal to somehow insert the IOAM data > immediately after the TCP header and before the TCP data. All of these > are attempts to use protocol headers that are thought to be most > palatable to intermediate devices and maximize the chances of > efficient delivery. > > IMO, all of the aforementioned techniques have some problem or aren't > clean (including the GRE solution). The best solution, and most > architecturally correct and generic one, is an IOAM option in > Hop-by-Hop extension headers. > > Tom > > > > > > > Thanks > > > > Heidi > > > > > > > > From: Vijay Rangarajan <vijayr@arista.com> > > Date: Thursday, August 22, 2019 at 7:22 AM > > To: "Frank Brockners (fbrockne)" <fbrockne@cisco.com> > > Cc: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>, Jai Kumar < > jai.kumar@broadcom.com>, "draft-ietf-ippm-ioam-data@ietf.org" < > draft-ietf-ippm-ioam-data@ietf.org>, IETF IPPM WG <ippm@ietf.org>, Hugh > Holbrook <holbrook@arista.com>, Anoop Ghanwani <Anoop.Ghanwani@dell.com>, > "OU, Heidi" <heidi.ou@alibaba-inc.com>, Surendra Anubolu < > surendra.anubolu@broadcom.com>, John Lemon <john.lemon@broadcom.com> > > Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 > > > > > > > > Hi Frank: > > > > Thanks, I knew I was missing something. > > > > So basically what you are saying is - let's say we have a UDP packet, we > are just going to stick in the GRE header and IOAM Header and Metadata > in-between the original IP and UDP headers? > > > > > > > > So, the next protocol in the IOAM Header should indicate the L4 protocol > - i.e UDP/TCP? > > > > Looking at https://datatracker.ietf.org/doc/draft-weis-ippm-ioam-eth/, > it actually defines the "Next protocol" in the IOAM header to be an > ethertype value? > > > > > > > > Thanks, > > > > Vijay > > > > > > > > > > > > On Thu, Aug 22, 2019 at 6:22 PM Frank Brockners (fbrockne) < > fbrockne@cisco.com> wrote: > > > > Hi Vijay, > > > > > > > > note that you don’t necessarily need to “tunnel” – you can just use the > GRE header to sequence-in IOAM. > > > > > > > > Cheers, Frank > > > > > > > > From: Vijay Rangarajan <vijayr@arista.com> > > Sent: Donnerstag, 22. August 2019 05:31 > > To: Carlos Pignataro (cpignata) <cpignata@cisco.com> > > Cc: Jai Kumar <jai.kumar@broadcom.com>; > draft-ietf-ippm-ioam-data@ietf.org; IETF IPPM WG <ippm@ietf.org>; Frank > Brockners (fbrockne) <fbrockne@cisco.com>; Hugh Holbrook < > holbrook@arista.com>; Anoop Ghanwani <Anoop.Ghanwani@dell.com>; OU, Heidi > <heidi.ou@alibaba-inc.com>; Surendra Anubolu < > surendra.anubolu@broadcom.com>; John Lemon <john.lemon@broadcom.com> > > Subject: Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 > > > > > > > > Thanks Carlos, for pointing me to the draft. > > > > > > > > Based on my understanding of the two drafts I have the following > questions and concerns: > > > > If I understand correctly, to deploy inband telemetry, we would need to > construct GRE tunnels coinciding with the IOAM domain? > > GRE typically requires configuration to provision the tunnels. > Provisioning and managing these tunnels and keeping these updated as the > network grows/shrinks could be a significant overhead. > > In order to get the benefit of telemetry, we are imposing a change in > forwarding protocol/topology and configuration - which, I feel is not > desirable. For example, a customer might have basic L3 routing enabled and > the expectation would be for inband telemetry to work seamlessly, without > having to revamp the network with GRE tunnels and such. This could be a > significant barrier to deployment. > > If sampling is used to select packets for performing IOAM encap, is the > expectation that only sampled IOAM packets go through GRE encap? Or all > data packets? > > Due to network nodes inserting the IOAM data, the inner L3/L4 headers > keep getting pushed deeper. I would imagine this gets challenging for ASICs > to access these fields for hashing/load balancing. > > Assuming only a subset of packets in a flow are subject to IOAM (based > on sampling), how do we ensure these packets take the same network path as > the rest of the packets in the flow? > > > > Thanks, > > > > Vijay > > > > > > > > > > > > On Wed, Aug 21, 2019 at 5:04 PM Carlos Pignataro (cpignata) < > cpignata@cisco.com> wrote: > > > > Hello, Vijay, > > > > > > > > Please see https://datatracker.ietf.org/doc/draft-weis-ippm-ioam-eth/, > and the document this replaces. > > > > > > > > Thanks! > > > > Thumb typed by Carlos Pignataro. > > > > Excuze typofraphicak errows > > > > > > 2019/08/21 6:35、Vijay Rangarajan <vijayr@arista.com>のメール: > > > > Hello all: > > > > Apologise if this has been previously discussed. > > > > In reading "draft-ietf-ippm-ioam-data-06", I don't see mention of GRE > encap. The draft, in fact in Sec 3, says the following - "The in-situ OAM > data field can be transported by a variety of transport protocols, > including NSH, Segment Routing, Geneve, IPv6, or IPv4. Specification > details for these different transport protocols are outside the scope of > this document." > > > > > > > > Is there another document, or a description somewhere, that talks about > how IOAM is proposed to be carried in GRE? what would be the GRE payload, > the GRE protocol type etc? > > > > > > > > Thanks, > > > > Vijay > > > > > > > > > > > > On Wed, Aug 21, 2019 at 7:52 AM Jai Kumar <jai.kumar@broadcom.com> > wrote: > > > > Hello Frank, > > > > > > > > This is in context of our conversation at IETF105. My goal is to provide > input and improve current IOAM data draft with the learnings we had with > IFA deployment. > > > > This feedback is based on various customer interactions and concerns > raised by them wrt IOAM. Each feedback is a longer topic and I am starting > this thread as a summary email. This is just highlighting the issues and > not yet proposing any solution. > > > > > > > > > > > > Feedback 1: > > > > Section 4.2..1 Pre-allocated and Incremental Trace Options > > > > Pre-allocated and incremental trace option is 8Bytes long. This can be > easily reduced to 4Bytes. > > > > There is a feedback that pre-allocated option is really not needed and > either be removed or made optional. > > > > Given that deployments are sensitive to the IOAM overhead (specially in > 5G deployments), it’s a 50% fixed overhead savings on a per packet basis. > > > > > > > > > > > > Feedback 2: > > > > Section 4.1 IOAM Namespaces > > > > Namespaces should be treated as templates (similar to IPFIX template > record formats). This is more flexible way of enumerating data. 64K > namespace id is a very large namespace and can be reduced to 64 IANA > specified name spaces. Separate private name space can be allowed instead > of interleaving of opaque data in the IANA allocated name space as > suggested in the current draft “opaque state snapshot”. > > > > https://tools.ietf.org/html/rfc7011#section-3.4 > > > > > > > > Feedback 3: > > > > Section 4.2.1 Pre-allocated and Incremental Trace Options > > > > IOAM-Trace-Type: A 24-bit identifier which specifies which data > > > > types are used in this node data list. > > > > This is the most contentious of all. In the current proposal, as new > data fields are added, there is a corresponding trace type bit need in the > header. This essentially means that all possible data fields need to be > enumerated. Given that we there are 64K names spaces allowed, I don’t see > how we can fit all possible data fields in this 24bit vector. I know there > was a suggestion of keeping last bit as an extension bit but it is still > scalable and/or easy to implement in hardware. Besides this the data fields > are not annotated/encoded with the data type, something like in IPFIX > https://tools.ietf.org/html/rfc7011#section-6.1 > > > > > > > > Feedback 4: > > > > There is no version field in the data header and this will make > interoperability challenging. Standard will evolve and headers bit > definition and/or trace type will change and without version field HW will > not be able to correctly handle the IOAM data headers. > > > > > > > > Feedback 5: > > > > Handling of TCP/UDP traffic using GRE encap is not acceptable. Here are > some of the issues I can think of > > > > GRE encaped IOAM packets will traverse a different network path then the > original packet > > Not all packets can be GRE encaped to avoid the previous problem, due to > wastage of network bandwidth (typically sampled traffic is used for IOAM). > What about native GRE traffic, will it get further encaped in another GRE > tunnel and so forth. > > IP header protocol will point to GRE IP proto and IOAM ethertype > (pending allocation by IEEE) need to be read from the GRE header to detect > an IOAM packet. This means parsing performance penalty for all regular GRE > (non IOAM) traffic. > > > > > > > > Thanks, > > > > -Jai > > > > > > > > _______________________________________________ > > ippm mailing list > > ippm@ietf.org > > https://www.ietf.org/mailman/listinfo/ippm > > _______________________________________________ > ippm mailing list > ippm@ietf.org > https://www.ietf.org/mailman/listinfo/ippm >
- [ippm] Review on draft-ietf-ippm-ioam-data-06 Jai Kumar
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Carlos Pignataro (cpignata)
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Vijay Rangarajan
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Frank Brockners (fbrockne)
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Vijay Rangarajan
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 OU, Heidi
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Tom Herbert
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 OU, Heidi
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Tom Herbert
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Barak Gafni
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Anoop Ghanwani
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Tom Herbert
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Greg Mirsky
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Jai Kumar
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Greg Mirsky
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Tom Herbert
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Tianran Zhou
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Tianran Zhou
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Anoop Ghanwani
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Jai Kumar
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Carlos Pignataro (cpignata)
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Frank Brockners (fbrockne)
- Re: [ippm] Review on draft-ietf-ippm-ioam-data-06 Anoop Ghanwani